Recently, semiconductor fabrication techniques require further fine patterning methods to satisfy the requirement of higher integration. Since there is a limitation to improving the resolution of exposing devices, however, the minimum line width and line space capable of being patterned also are limited.
When the pattern size is reduced to less than a micron, effects relating to the interference and diffraction of light become greater and resolution is decreased. Accordingly, when g-line (wave length of 436 nm) or i-line (wave length of 365 nm) light is used, it is very difficult to make a pattern with less than 0.5.mu. or 0.4.mu. as the minimum line width, respectively.
Heretofore, as illustrated in FIG. 1 (A), a pattern has been made (transcribed) in photo-resist 13 on layer 12 on silicon substrate 11 by exposing with light and removing exposed portions by means of an etching process. Thereafter, as illustrated in FIG. 1 (B), photo-resist 13 is used as a mask to pattern layer 12 by etching exposed portions of layer 12, and photo-resist 13 is thereafter removed.
The line width of this pattern is represented as "L", and the line space is "S".
With such a conventional patterning method, when g-line and i-line radiation are used, forming a pattern with less than 0.3 .mu. line width and line space is almost impossible due to the limited resolution of the exposing device and resist.